Internal combustion engine with common rail pilot and main injection

ABSTRACT

An internal combustion engine including a pilot subchamber, a pilot fuel injector having a tip in communication with the pilot subchamber, an ignition element positioned to ignite fuel within the pilot subchamber, and a main fuel injector spaced apart from the pilot fuel injector. The engine includes a common rail in fluid communication with the main fuel injector and with the pilot fuel injector and a pressure regulating mechanism in fluid communication with the common rail for regulating a fuel pressure therein. A method of combusting fuel in an internal combustion engine is also provided.

TECHNICAL FIELD

The application relates generally to internal combustion engines and,more particularly, to pilot and main fuel injection in such engines.

BACKGROUND OF THE ART

Some reciprocating internal combustion engines have a main and pilotfuel injection performed by a same fuel injector. The fuel injectors maybe fed by a common rail, where for example each injector includes apressure intensification mechanism to perform the main injection at anincreased pressure and performs a pilot injection using the common railpressure. Accordingly, a relatively complex configuration may berequired for each injector.

Some internal combustion engines, including some rotary engines, includea pilot subchamber for pilot ignition. However, known arrangements arenot optimized, in terms of combustion arrangements and characteristics,and thus room for improvement exists.

SUMMARY

In one aspect, there is provided an internal combustion enginecomprising: an outer body defining an internal cavity; a rotatable bodysealingly and rotationally received within the internal cavity to defineat least one combustion chamber of variable volume; a pilot subchamberdefined in the outer body in communication with the internal cavity; apilot fuel injector having a tip in communication with the pilotsubchamber; an ignition element positioned to ignite fuel within thepilot subchamber; a main fuel injector spaced apart from the pilot fuelinjector and having a tip in communication with the internal cavity at alocation spaced apart from the pilot subchamber; a common rail in fluidcommunication with the main fuel injector and with the pilot fuelinjector; and a pressure regulating mechanism in fluid communicationwith the common rail for regulating a fuel pressure therein.

In another aspect, there is provided a rotary internal combustion enginecomprising: an outer body having an internal cavity defined by twoaxially spaced apart end walls and a peripheral wall extending betweenthe end walls; a rotor body rotatable within the internal cavity insealing engagement with the peripheral and end walls and defining atleast one chamber of variable volume in the internal cavity around therotor body; a pilot subchamber defined in the outer body in fluidcommunication with the internal cavity; a pilot fuel injector having atip in communication with the pilot subchamber; an ignition elementpositioned to ignite fuel within the pilot subchamber; a main fuelinjector spaced apart from the pilot fuel injector, the main fuelinjector having a tip in communication with the internal cavity at alocation spaced apart from the pilot subchamber; a common rail in fluidcommunication with the main fuel injector and with the pilot fuelinjector; and a pressure regulating mechanism in fluid communicationwith the common rail for regulating a fuel pressure therein.

In a further aspect, there is provided a method of combusting fuel in aninternal combustion engine having a rotatable body defining at least onecombustion chamber, the method comprising: pressurizing the fuel in acommon rail; feeding a pilot injector with the common rail to injectfuel in a pilot subchamber; igniting the fuel within the pilotsubchamber; circulating the ignited fuel out of the pilot subchamber andinto one of the at least one combustion chamber; and feeding a maininjector separate from the pilot injector with the common rail to injectfuel into the one of at least one combustion chamber spaced apart fromthe pilot subchamber and the pilot injector.

DESCRIPTION OF THE DRAWINGS

Reference is now made to the accompanying figures in which:

FIG. 1 is a schematic cross-sectional view of a rotary internalcombustion engine in accordance with a particular embodiment;

FIG. 2 is a schematic view of an injection system which can be used withan internal combustion engine such as shown in FIG. 1, in accordancewith a particular embodiment;

FIG. 3 is a schematic view of an injection system which can be used withan internal combustion engine such as shown in FIG. 1, in accordancewith another particular embodiment; and

FIG. 4 is a schematic view of an injection system which can be used withan internal combustion engine such as shown in FIG. 1, in accordancewith a further particular embodiment.

DETAILED DESCRIPTION

Referring to FIG. 1, a rotary internal combustion engine 10 known as aWankel engine is schematically shown. In a particular embodiment, therotary engine 10 is used in a compound cycle engine system such asdescribed in Lents et al.'s U.S. Pat. No. 7,753,036 issued Jul. 13,2010, as described in Julien et al.'s U.S. Pat. No. 7,775,044 issuedAug. 17, 2010, or as described in U.S. patent application Ser. Nos.13/554,517 and 13/554,564 both filed Jul. 20, 2012, the entire contentsof all of which are incorporated by reference herein. The compound cycleengine system may be used as a prime mover engine, such as on anaircraft or other vehicle, or in any other suitable application. In anyevent, in such a system, air is compressed by a compressor beforeentering the Wankel engine, and the engine drives one or more turbine(s)of the compound engine. In another embodiment, the rotary engine 10 isused with a turbocharger without being compounded; in anotherembodiment, the rotary engine 10 is used without a turbocharger, withair at atmospheric pressure, as a stand-alone engine. In one embodiment,the rotary engine 10 may be applicable to land base systems including,but not limited to, generators.

The engine 10 is shown and described herein as a Wankel engine as anexample only. It is understood that the engine 10 may alternately be anyother adequate type of internal combustion engine having a pilotsubchamber for ignition, such as for example a reciprocating engine, ora rotary engine having a different configuration than that of a Wankelengine. For example, in a particular embodiment, the rotary engine maybe a single or eccentric type rotary engine in which the rotor rotatesabout a fixed center of rotation. For example, the rotary engine may bea sliding vane engine, such as described in U.S. Pat. No. 5,524,587issued Jun. 11, 1996 or in U.S. Pat. No. 5,522,356 issued Jun. 4, 1996,the entire contents of both of which are incorporated by referenceherein. In another particular embodiment, the rotary engine may be anoscillatory rotating engine, including two or more rotors rotating atdifferent angular velocities, causing the distance between portions ofthe rotors to vary and as such the chamber volume to change. In anotherparticular embodiment, the rotary engine may be a planetary rotatingengine having a different geometry than that of the Wankel engine, suchas for example a planetary engine having a rotor cavity with anepitrochoid profile defining three lobes and a rotor with four apexportions. Examples of such non-Wankel rotary engines are shown inApplicant's U.S. application Ser. No. 14/796,185 filed Jan. 25, 2013,the entire contents of which is incorporated by reference herein. Otherrotary engine geometries are also possible.

The engine 10 generally includes at least one moveable body received ina corresponding internal cavity of an outer body to define at least onecombustion chamber. For example, the engine 10 may be a reciprocatingengine with a plurality of internal cavities each receiving a moveablebody in the form of a reciprocating piston. The engine 10 mayalternately be a rotary engine with a plurality of internal cavitieseach receiving a moveable body on the form of a rotatable body or rotor.

Referring back to FIG. 1, in the particular embodiment shown, the engine10 comprises an outer body 12 having at least one rotor cavity 20 (onlyone of which is shown) each defined by axially-spaced end walls 14 and aperipheral wall 18 extending therebetween, with a rotatable body orrotor 24 received in each cavity 20. The inner surface 19 of theperipheral wall 18 of each cavity 20 has a profile defining two lobes,which is preferably an epitrochoid.

In the case of a multiple rotor engine, the outer body 12 may beintegral or defined by a plurality of body portions each defining arespective one of the cavities 20 and receiving a respective one of therotors 24.

Each rotor 24 is received within the respective cavity 20, with thegeometrical axis of the rotor 24 being offset from and parallel to theaxis of the outer body 12. Each rotor 24 has axially spaced end faces 26adjacent to the outer body end walls 14, and a peripheral face 28extending therebetween. The peripheral face 28 defines threecircumferentially-spaced apex portions 30 and a generally triangularprofile with outwardly arched sides. The apex portions 30 are in sealingengagement with the inner surface of peripheral wall 18 to form threerotating working or combustion chambers 32 between the inner rotor 24and outer body 12. A recess (not shown) is defined in the peripheralface 28 of the rotor 24 between each pair of adjacent apex portions 30,to form part of the corresponding chamber 32.

The combustion chambers 32 are sealed. Each rotor apex portion 30 has anapex seal 52 extending from one end face 26 to the other and protrudingradially from the peripheral face 28. Each apex seal 52 is biasedradially outwardly against the peripheral wall 18 through a respectivespring. An end seal 54 engages each end of each apex seal 52, and isbiased against the respective end wall 14 through a suitable spring.Each end face 26 of the rotor 24 has at least one arc-shaped face seal60 running from each apex portion 30 to each adjacent apex portion 30,adjacent to but inwardly of the rotor periphery throughout its length. Aspring urges each face seal 60 axially outwardly so that the face seal60 projects axially away from the adjacent rotor end face 26 intosealing engagement with the adjacent end wall 14 of the cavity. Eachface seal 60 is in sealing engagement with the end seal 54 adjacent eachend thereof.

Although not shown, each rotor 24 is journaled on an eccentric portionof a shaft and includes a phasing gear co-axial with the rotor axis,which is meshed with a fixed stator phasing gear secured to the outerbody co-axially with the shaft. In a particular embodiment where theengine 10 includes multiple rotors 24 and cavities 20, each rotor 24 maybe journaled on a respective eccentric portion of a same shaft. Theshaft rotates each rotor 24 and the meshed gears guide the rotor 24 toperform orbital revolutions within the respective rotor cavity 20. Theshaft rotates three times for each complete rotation of the rotor 24 asit moves around the rotor cavity 20. Oil seals are provided around thephasing gear to prevent leakage flow of lubricating oil radiallyoutwardly thereof between the respective rotor end face 26 and outerbody end wall 14.

For each rotor cavity 20, at least one inlet port 44 is defined throughone of the end walls 14 or the peripheral wall 18 for admitting air(atmospheric or compressed) into one of the working chambers 32, and atleast one exhaust port 46 is defined through one of the end walls 14 orthe peripheral wall 18 for discharge of the exhaust gases from thecombustion chambers 32. The inlet and exhaust ports 44, 46 arepositioned relative to each other and relative to the ignition memberand fuel injectors (further described below) such that during eachrotation of the rotor 24, each chamber 32 moves around the cavity 20with a variable volume to undergo the four phases of intake,compression, expansion and exhaust, these phases being similar to thestrokes in a reciprocating-type internal combustion engine having afour-stroke cycle.

In a particular embodiment, the inlet and exhaust ports 44, 46 arearranged such that the rotary engine 10 operates under the principle ofthe Miller or Atkinson cycle, with its volumetric compression ratiolower than its volumetric expansion ratio. In another embodiment, theinlet and exhaust ports 44, 46 are arranged such that the volumetriccompression and expansion ratios are equal or similar to one another.

The engine 10 includes a pilot subchamber 72 for each rotor cavity 20,defined in the outer body 12, for pilot fuel injection and ignition. Inthe embodiment shown, the pilot subchamber 72 is provided in an insert34 received in a corresponding hole 36 defined through the peripheralwall 18 of the outer body 12. The insert 34 is retained to theperipheral wall 18 using any adequate type of connection, including, butnot limited to, fasteners, welding, brazing, retention through a coveroverlapping the insert 34 and connected to the peripheral wall 18, etc.In another embodiment, the pilot subchamber 72 is directly defined inthe peripheral wall 18.

In the embodiment shown, the insert body 34 has the entire pilotsubchamber 72 defined therein, shown here with a circular cross-section.Other geometries are also possible, including but not limited tocylindrical, conical, frustoconical, wedge-shaped profiles, etc. Theinsert 34 includes at least one outlet opening 74 defined therein forcommunication with the cavity 20, and the subchamber 72 has a shapeforming a reduced cross-section adjacent the opening(s) 74, such thatthe opening(s) 74 define a restriction to the flow between thesubchamber 72 and the cavity 20. The opening(s) 74 may have variousshapes and/or be defined by a pattern of multiple holes.

The particular insert 34 shown is provided only as an example, and it isunderstood that other geometries and/or positions within the peripheralwall 18 are possible for the insert 34. In a particular embodiment, theinsert 34 is made of a material having a greater high temperatureproperties and/or lower thermal conductivity than that of the peripheralwall 18, which may be for example made of aluminum. In one embodiment,the insert 34 is made of a nickel or cobalt based super alloy.Alternately, as mentioned above, the insert 34 may be omitted and thepilot subchamber 72 be directly defined in the peripheral wall 18 if theperipheral wall 18 is made of a material having sufficient heatresistance and adequate high temperature properties to resist the hightemperatures within the subchamber 72.

The peripheral wall 18 of each rotor cavity 20 has a main injectorelongated hole 40 defined therethrough, in communication with the rotorcavity 20 and spaced apart from the pilot subchamber 72. A main fuelinjector 42 is received and retained within this corresponding hole 40,with the tip of the main injector 42 communicating with the cavity 20 ata point spaced apart from the pilot subchamber 72. The main injector 42is located rearwardly of the pilot subchamber 72 with respect to thedirection R of the rotor rotation and revolution, and is angled todirect fuel forwardly into each of the rotating chambers 32 sequentiallywith a tip hole pattern designed for an adequate spray.

The peripheral wall 18 of each rotor cavity 20 also has a pilot injectorelongated hole 76 defined therethrough in communication with thesubchamber 72. A pilot fuel injector 78 is received and retained withinthe corresponding hole 76, with the tip of the pilot injector 78 beingin communication with the subchamber 72, for example by terminating in acorresponding opening defined in the insert 34 between the subchamber 72and the pilot injector hole 76. It can be seen that the main injector 42and pilot injector 78 are spaced apart from one another.

The pilot injector 78 and main injector 42 of each rotor cavity 20inject fuel, which in a particular embodiment is heavy fuel e.g. diesel,kerosene (jet fuel), equivalent biofuel, etc. into the chambers 32.Alternately, the fuel may be any other adequate type of fuel suitablefor injection as described, including non-heavy fuel such as for examplegasoline or liquid hydrogen fuel. In a particular embodiment, at least0.5% and up to 20% of the fuel is injected through the pilot injector78, and the remainder is injected through the main injector 42. Inanother particular embodiment, at most 10% of the fuel is injectedthrough the pilot injector 78. In another particular embodiment, at most5% of the fuel is injected through the pilot injector 78. The maininjector 42 injects the fuel such that each rotating chamber 32 when inthe combustion phase contains a lean mixture of air and fuel.

The peripheral wall 18 of each rotor cavity 20 and, in the embodimentshown, the insert body 34 have an ignition element elongated hole 82defined therein in communication with the subchamber 72. An ignitionelement 84 is received and retained within the corresponding hole 82 andpositioned to ignite fuel within the subchamber 72, e.g. with the tip ofthe ignition element 84 being received in the subchamber 72. In theembodiment shown, the ignition element 84 is a glow plug. Otherconfigurations are also possible, including for example having theignition element 84 completely received within the insert 34, and/orignition element(s) 84 of any other adequate type, including but notlimited to plasma ignition, laser ignition, spark plug, microwave, othertypes of ignition elements, etc.

Referring to FIG. 2, in a particular embodiment, the main fuelinjector(s) 42 and the pilot fuel injector(s) 78 of the engine 10 are influid communication with a same common rail 100. The common rail 100 hasan the inlet 108 in fluid communication with a pump system 106. In theembodiment shown, the pump system 106 includes a low pressure pump 110located in or in fluid communication with a fuel source or fuel tank112, and a high pressure pump 114 receiving the fuel from the lowpressure pump 110 and feeding it to the inlet 108 of the common rail100.

The common rail 100 has an outlet 116 in selective fluid communication,directly or indirectly, with the fuel tank 112 such as to return anexcess of fuel thereto. In the embodiment shown, a metering or pressureregulating valve 118 is provided at the outlet 116 to regulate the flowof fuel therethrough. A pressure regulating mechanism regulates the fuelpressure in the common rail and may be provided in the pump system 106(e.g. metering unit) and/or by the valve 118.

In the embodiment shown, an engine control unit 120 controls the pilotand main fuel injection through control of the high pressure pump 114(e.g. actuation, fuel pressure and/or fuel flow), the valve 118 (e.g.position) and the fuel injectors 42, 78 (e.g. actuation of electronicvalves controlling the injection pulses).

In a particular embodiment, the engine 10 has a single moveable body,with a single main injector 42 and a single pilot injector 78 in fluidcommunication with the common rail 100. In another embodiment, theengine 10 includes at least one additional moveable body, each having anadditional main injector 42 and an additional pilot injector 78 (onebeing shown in dotted lines in FIG. 2) also in fluid communication withthe same common rail 100.

In use, the fuel is combusted by pressurizing the fuel in the commonrail 100, feeding the pilot injector(s) 78 with the common rail 100 toinject the fuel in the pilot subchamber(s) 72 where it is ignited andcirculated into a respective combustion chamber 32, and feeding the maininjector(s) 42 with the common rail 100 to inject the fuel into thecombustion chamber 32. The pilot and main injections are thus performedspaced apart from one another.

In a particular embodiment, both the main and pilot injectors 42, 78inject the fuel using the pressure provided in the common rail 100, e.g.without the use of pressure intensification mechanisms. In a particularembodiment, a difference in fuel volume between the pilot and maininjections may be provided by tuning the duration and/or number ofinjection pulses and/or by using a pilot injector 78 having a smalleropen area, as defined by the tip openings through which the fuel isinjected, than that of the main injector 42.

In the embodiment shown in FIG. 3, the engine 10 includes multiplemoveable bodies, and as such a plurality of main fuel injectors 42 andpilot fuel injectors 78 (three in the embodiment shown). All the mainfuel injectors 42 are in fluid communication with a same common primaryfuel conduit 202, while all the pilot fuel injectors 45 are in fluidcommunication with a same common secondary fuel conduit 204. A primarypressure regulating mechanism regulates the fuel pressure in the primaryfuel conduit 202 while a secondary pressure regulating mechanismregulates a fuel pressure in the secondary conduit 204. The primary andsecondary pressure regulating mechanisms are settable at differentpressure values from one another such that the primary and secondaryfuel conduits 202, 204 can provide fuel at different pressures.

In the particular embodiment shown, the primary and secondary conduits202, 204 are separate chambers defined side by side in a same commonrail 200. The inlet 208 of the common rail 200 and of the primary fuelconduit 202 is in fluid communication with a pump system 206 (e.g.single or multiple pump arrangement) providing for the primary pressureregulating mechanism (e.g. through a metering unit), by regulating thefuel flow from the pump system 206 to the primary conduit 202.

The primary and secondary conduits 202, 204 are in selective fluidcommunication with each other through a metering or pressure regulatingvalve 222 which is also in selective fluid communication with the fueltank 112 such as to return an excess of fuel thereto. In a particularembodiment, the valve 222 is a metering valve. The secondary conduit 204has an outlet 216 (also corresponding to the outlet of the common rail200) in selective fluid communication, directly or indirectly, with thefuel tank 112 such as to return an excess of fuel thereto. In theembodiment shown, a second metering or pressure regulating valve 218 isprovided at the outlet of the secondary conduit to regulate the flow offuel therethrough. As such, in the embodiment shown, the pressureregulating mechanism of the secondary conduit 204 may be provided by theinlet valve 222 and/or the outlet valve 218.

In the embodiment shown, the engine control unit 120 controls the pilotand main fuel injection through control of the pump system 206 (e.g.actuation, fuel pressure and/or fuel flow), the valves 218, 222 (e.g.position) and the fuel injectors 42, 78 (e.g. actuation of electronicvalves controlling the injection pulses).

In a particular embodiment, the different pressures of the main andpilot injection allows for main and pilot injectors 42, 78 having asimilar size and configuration to be used while still obtaining asmaller fuel volume in the pilot injection than in the main injection.Alternately, as above, the pilot injector 78 may have a smaller openarea, as defined by the tip openings through which the fuel is injected,than that of the main injector 42.

In use, the fuel is combusted by pressurizing the fuel in the primaryand secondary conduits 202, 204 to obtain different fuel pressures,feeding the pilot injectors 78 with the primary conduit 202 to injectfuel in the respective pilot subchamber 72 where it is ignited andcirculated into a respective combustion chamber 32, and feeding the maininjectors 42 with the secondary conduit 204 to inject fuel into thecombustion chamber 32.

Alternately, the primary conduit 202 may be connected to the maininjectors 42 and the secondary conduit 204 may be connected to the pilotinjectors 78.

The embodiment shown in FIG. 4 is similar to the embodiment shown inFIG. 3. However, in this embodiment, the primary and secondary conduits302, 304 are respectively defined by separate common rails. A first pumpsystem 306 (e.g. single or multiple pump arrangement) is in fluidcommunication with the fuel source and with the inlet 308 of the primaryconduit. A second pump system 307 (e.g. single or multiple pumparrangement) is in fluid communication with the fuel tank 112 and withthe inlet 309 of the secondary conduit 304.

Each conduit 302, 304 has an outlet 315, 316 in selective fluidcommunication, directly or indirectly, with the fuel tank 112 such as toreturn an excess of fuel thereto. In the embodiment shown, a metering orpressure regulating valve 322, 318 is provided at the outlet 315, 316 ofeach conduit 302, 304 to regulate the flow of fuel therethrough. Theprimary pressure regulating mechanism may thus provided in the firstpump system 306 (e.g. metering unit) and/or by the first valve 322,while the secondary pressure regulating mechanism may be provided in thesecond pump system 307 (e.g. metering unit) and/or by the second valve318.

In the embodiment shown, the engine control unit 120 controls the pilotand main fuel injection through control of the pump systems 306, 307(e.g. actuation, fuel pressure and/or fuel flow), the valves 318, 322(e.g. position) and the fuel injectors 42, 78 (e.g. actuation ofelectronic valves controlling the injection pulses). Alternately, thepump system and valve associated with each of the conduits may becontrolled by a different engine control unit.

The above description is meant to be exemplary only, and one skilled inthe art will recognize that changes may be made to the embodimentsdescribed without departing from the scope of the invention disclosed.Modifications which fall within the scope of the present invention willbe apparent to those skilled in the art, in light of a review of thisdisclosure, and such modifications are intended to fall within theappended claims.

1. An internal combustion engine comprising: an outer body defining aninternal cavity; a rotatable body sealingly and rotationally receivedwithin the internal cavity to define at least one combustion chamber ofvariable volume; a pilot subchamber defined in the outer body incommunication with the internal cavity; a pilot fuel injector having atip in communication with the pilot subchamber; an ignition elementpositioned to ignite fuel within the pilot subchamber; a main fuelinjector spaced apart from the pilot fuel injector and having a tip incommunication with the internal cavity at a location spaced apart fromthe pilot subchamber; a common rail in fluid communication with the mainfuel injector and with the pilot fuel injector; and a pressureregulating mechanism in fluid communication with the common rail forregulating a fuel pressure therein.
 2. The engine as defined in claim 1,wherein the pressure regulating mechanism is provided at least in partin a pump in fluid communication with a fuel source and with an inlet ofthe common rail.
 3. The engine as defined in claim 2, wherein thepressure regulating mechanism includes a metering or pressure regulatingvalve through which a fuel outlet of the common rail is in selectivefluid communication with the fuel source.
 4. The engine as defined inclaim 3, wherein the valve is actuable by an engine control unit.
 5. Theengine as defined in claim 1, wherein the internal cavity is defined bytwo axially spaced apart end walls and a peripheral wall extendingbetween the end walls, and the rotatable body is a rotor body rotatablewithin the internal cavity in sealing engagement with the peripheral andend walls.
 6. The engine as defined in claim 5, wherein the internalcavity defines an epitrochoid shape with two lobes, the rotor body hasthree circumferentially spaced apex portions, and the at least onecombustion chamber include three rotating chambers of variable volume,the rotor body being engaged to an eccentric portion of a shaft torotate and perform orbital revolutions within the cavity with each ofthe apex portions remaining in sealing engagement with the peripheralwall and separating the chambers.
 7. The engine as defined in claim 1,wherein the pilot injector and the main injector have tip openingsthrough which the fuel is injected, and an open area defined by the tipopenings of the pilot injector is smaller than that defined by the tipopenings of the main injector.
 8. The engine as defined in claim 1,wherein the engine includes at least one additional rotatable bodysealingly and rotationally received within a respective additionalinternal cavity of the outer body to define at least one combustionchamber of variable volume, and further including, for each additionalrotatable body, a respective additional pilot subchamber defined in theouter body in communication with the respective additional internalcavity, an additional pilot fuel injector having a tip in communicationwith the respective additional pilot subchamber, an additional ignitionelement positioned to ignite fuel within the respective additional pilotsubchamber, and an additional main fuel injector having a tip incommunication with the respective additional internal cavity at alocation spaced apart from the respective additional pilot subchamber,the common rail also being in fluid communication with the additionalmain fuel injector and with the additional pilot fuel injector of eachadditional rotatable body.
 9. A rotary internal combustion enginecomprising: an outer body having an internal cavity defined by twoaxially spaced apart end walls and a peripheral wall extending betweenthe end walls; a rotor body rotatable within the internal cavity insealing engagement with the peripheral and end walls and defining atleast one chamber of variable volume in the internal cavity around therotor body; a pilot subchamber defined in the outer body in fluidcommunication with the internal cavity; a pilot fuel injector having atip in communication with the pilot subchamber; an ignition elementpositioned to ignite fuel within the pilot subchamber; a main fuelinjector spaced apart from the pilot fuel injector, the main fuelinjector having a tip in communication with the internal cavity at alocation spaced apart from the pilot subchamber; a common rail in fluidcommunication with the main fuel injector and with the pilot fuelinjector; and a pressure regulating mechanism in fluid communicationwith the common rail for regulating a fuel pressure therein.
 10. Theengine as defined in claim 9, wherein the internal cavity defines anepitrochoid shape with two lobes, the rotor body has threecircumferentially spaced apex portions, and the at least one combustionchamber include three rotating chambers of variable volume, the rotorbody being engaged to an eccentric portion of a shaft to rotate andperform orbital revolutions within the cavity with each of the apexportions remaining in sealing engagement with the peripheral wall andseparating the chambers.
 11. The engine as defined in claim 9, whereinthe pressure regulating mechanism is provided at least in part in a pumpin fluid communication with a fuel source and with an inlet of thecommon rail.
 12. The engine as defined in claim 11, wherein the pressureregulating mechanism includes a metering or pressure regulating valvethrough which a fuel outlet of the common rail is in selective fluidcommunication with the fuel source.
 13. The engine as defined in claim12, wherein the valve is actuable by an engine control unit.
 14. Theengine as defined in claim 9, wherein the pilot injector and the maininjector have tip openings through which the fuel is injected, and anopen area defined by the tip openings of the pilot injector is smallerthan that defined by the tip openings of the main injector.
 15. Theengine as defined in claim 9, wherein the engine includes at least oneadditional rotor body engaged to a same shaft as the rotor body, theadditional rotor body being in sealing engagement with peripheral andend walls of a respective additional internal cavity of the outer bodyto define at least one combustion chamber of variable volume, andfurther including, for each additional rotor body, a respectiveadditional pilot subchamber defined in the outer body in communicationwith the respective additional internal cavity, an additional pilot fuelinjector having a tip in communication with the respective additionalpilot subchamber, an additional ignition element positioned to ignitethe fuel within the respective additional pilot subchamber, and anadditional main fuel injector spaced apart from the additional pilotfuel injector and having a tip in communication with the respectiveadditional cavity at a location spaced apart from the respective pilotsubchamber, the common rail also being in fluid communication with theadditional main fuel injector and with the additional pilot fuelinjector of each additional rotor body.
 16. A method of combusting fuelin an internal combustion engine having a rotatable body defining atleast one combustion chamber, the method comprising: pressurizing thefuel in a common rail; feeding a pilot injector with the common rail toinject fuel in a pilot subchamber; igniting the fuel within the pilotsubchamber; circulating the ignited fuel out of the pilot subchamber andinto one of the at least one combustion chamber; and feeding a maininjector separate from the pilot injector with the common rail to injectfuel into the one of at least one combustion chamber spaced apart fromthe pilot subchamber and the pilot injector.
 17. The method as definedin claim 16, wherein the internal combustion engine further comprises atleast one additional rotatable body each defining at least onecombustion chamber, the method further comprising, for each additionalrotatable body: feeding a respective additional pilot injector with thecommon rail to inject fuel in a respective additional pilot subchamber;igniting the fuel within the respective additional pilot subchamber;circulating the ignited fuel out of the respective additional pilotsubchamber and into one of the at least one combustion chamber definedby the additional rotatable body; and feeding a respective additionalmain injector separate from the respective additional pilot injectorwith the common rail to inject fuel into the one of at least onecombustion chamber defined by the additional rotatable body spaced apartfrom the respective additional pilot subchamber and the respectiveadditional pilot injector.
 18. The method as defined in claim 16,wherein the fuel is heavy fuel.
 19. The method as defined in claim 16,wherein pressurizing the fuel in the common rail includes regulating afuel pressure in the common rail with an engine control unit.
 20. Themethod as defined in claim 16, wherein injecting the fuel in the pilotsubchamber and injecting the fuel into the one of at least onecombustion chamber are performed at a same fuel pressure.